I'm working on a friends Bartell 48" power trowel and I can't identify this engine. I called Bartell and they say the serial number of the machine is to old and has been purged from their system. Only thing I can identify is the carburetor. Its a Makuni BV24. Here is some pictures of the motor.
Thanks Rivet you were spot on. Found a replacement carb on Amazon. It's a china one but parts for mini carb are crazy. If you can find them. Appreciate your help